Line 2 upside down baking sheets with a silicone mat or parchment paper (circle template optional but recommended).
Place a medium/large round piping tip (2A) in a large piping bag. Twist the bag right behind the tip and add a clip to seal off the opening. Place the bag tip down into either a clean tall cup with the edges folded over the rim to keep the bag open, or clip it into a bag holder.
Using a kitchen scale, carefully weigh out and sift the confectioner’s sugar and almond flour into a medium mixing bowl. Whisk well to fully blend the two together.
Place egg whites, granulated sugar, and cream of tartar into a large mixing bowl, and begin beating with a whisk attachment using either a handheld mixer or a stand mixer for 2 minutes on a medium low speed (Kitchen Aid Speed 4).
Turn up the mixer to a medium speed (Kitchen Aid Speed 6) and beat for an additional 2 minutes.
Add the gel food coloring.
Turn the mixer up to medium high speed (Kitchen Aid Speed 8) and beat for 3 more minutes, or until peaks are very stiff and the meringue clumps up in a ball in the center of the whisk. Test stiffness by removing the whisk and pointing it upward. (See photo in post) Once the peaks can hold their shape flipped upright, your meringue is ready.
Pour half of the almond flour/confectioner’s sugar mixture into the bowl with the meringue, and fold 15 times. One fold is scraping all the way around the edge of the batter in the bowl, and then pressing your spatula through the middle. Be sure to scoop around the bottom of the bowl and lift as well so you don’t miss any dry ingredients.
Pour in the remaining powdered sugar and almond flour, and continue folding (approximately 30 more folds) until dry ingredients are fully incorporated, the batter is no longer clumpy and stiff. Do not overfold. Please note this recipe stays a bit thicker than most, and should not be folded to the traditional figure 8 test consistency. Start checking your batter’s readiness every 5 folds or so at this point by scraping all batter down to the bottom of your bowl, and then wiggling your bowl back and forth several times. If the batter levels out with a few subtle peaks and lines remaining, it should be ready. The batter should not be completely flat/smooth, this is what it looks like when it's over mixed. (See photos of correct batter consistency in Basic French Macarons post for reference.)
Pour batter into the prepared piping bag, and twist the opening off. Hold your bag at the twist between your thumb and pointer finger. Remove the clip by the tip.
Holding the piping bag straight up and down, apply pressure to begin piping your batter in the center of your circle templates, releasing pressure once you are a few millimeters short of your desired size. After you release pressure, use a small quick circular flick to release your tip from the piped macaron.
Once you’ve piped a full tray, firmly bang the tray on the counter a few times to pop any air bubbles and smooth out shells. Pop any remaining large bubbles with a toothpick. Repeat with the second tray immediately.
Begin preheating your oven to 300℉, using an oven thermometer if possible to ensure accurate temperature readings.
Set aside shells to dry until they form a skin and are no longer tacky to the touch. Once you can gently run a finger over your shells, they are ready to bake. Use a fan to speed up the process, rotating the tray every few minutes to ensure even drying. This usually takes at least 16-20 minutes for me even with a fan.
Once the shells are dry, and the oven has fully preheated to 300℉, place one tray in the center of the middle rack of the oven. Bake for 18 minutes.
Quickly open door to check the shell’s doneness by gently pressing on the side just above the feet to see if it’s firm. If it moves at all, rotate the tray and bake for another 2 minutes.
Check shells by performing the same test, pressing on the side. If they are still unstable, bake for one more minute, and check again. Repeat until shells are firm and do not budge.
Repeat the bake with the second tray.
Allow shells to cool completely, and then carefully remove them from the silicone mat or parchment paper by gently peeling them off.